A systematic evaluation of the behavioral pharmacology of caffeine is planned. Dose-effect curves will be established for three behavioral activities or situations: mult FR FI; vigorous exercise; situations involving noxious or suppressing simuli. Effects in three species will be compared: mice; squirrel monkeys; macaques. The dose-effect curves for cardiovascular effects will be determined in monkeys, and the joint effects of the behavioral activities and caffeine on cardiovascular function. The effects of caffeine will be compared to those of other methylxanthines and to amphetamine.